U.S. patent application number 10/956055 was filed with the patent office on 2005-05-12 for method for judging road surface condition and device thereof, and program for judging road surface condition.
Invention is credited to Nakao, Yukio.
Application Number | 20050102086 10/956055 |
Document ID | / |
Family ID | 34431304 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050102086 |
Kind Code |
A1 |
Nakao, Yukio |
May 12, 2005 |
Method for judging road surface condition and device thereof, and
program for judging road surface condition
Abstract
A judgment method of road surface condition includes steps of:
periodically detecting the wheel rotational speeds of the four
wheel tires of a vehicle, memorizing the wheel rotational speed of
each of tires, determining a slip ratio from said wheel rotational
speeds, determining the acceleration or deceleration of the
vehicle, determining a relation equation between said slip ratio
and the acceleration or deceleration of the vehicle, determining a
judgment value for judging a friction coefficient between the road
surface and tires based on the slope of said relation equation
determined, and setting a threshold which is used for judging the
friction coefficient from the judgment value using the information
of wireless tags which were buried in the tires.
Inventors: |
Nakao, Yukio; (Kobe-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
34431304 |
Appl. No.: |
10/956055 |
Filed: |
October 4, 2004 |
Current U.S.
Class: |
701/80 ; 73/105;
73/9 |
Current CPC
Class: |
G01N 19/02 20130101;
B60T 8/172 20130101; B60T 2210/12 20130101 |
Class at
Publication: |
701/080 ;
073/009; 073/105 |
International
Class: |
G06F 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2003 |
JP |
2003-376710 |
Claims
What is claimed is:
1. A method for judging road surface condition comprising the steps
of: detecting periodically rotational speeds of four wheel tires
mounted on a vehicle; memorizing the rotational speed of each
tires; determining a slip ratio from said wheel rotational speeds;
determining acceleration or deceleration of said vehicle;
determining a relation equation between said slip ratio and said
acceleration of the vehicle; determining a judgment value for
judging a friction coefficient between road surface and said tires
based on slope of said relation equation determined; and setting a
threshold used for judging friction coefficient from said judgment
value with information of wireless tags buried in said tires.
2. The method for judging road surface condition of claim 1 further
comprising a step of judging abrasion condition of said tires by
comparison of said threshold with said judgment value.
3. A device for judging road surface condition comprising: a wheel
speed-detecting means for periodically detecting wheel rotational
speeds of four wheel tires of a vehicle; a memory means for
memorizing said wheel rotational speed of each tires; a slip
ratio-calculating means for determining a slip ratio from said
wheel rotational speeds; an acceleration deceleration-calculating
means for determining acceleration or deceleration of said vehicle;
a relation equation-calculating means for determining a relation
equation between said slip ratio and said acceleration of said
vehicle; a judgment value-calculating means for determining a
judgment value for judging a friction coefficient between road
surface and tires based on slope of said relation equation
determined; and a threshold-setting means for setting a threshold
used for judging friction coefficient from said judgment value with
information of wireless tags buried in said tires.
4. The device for judging road surface condition of claim 3 further
comprising an abrasion-judging means for judging the abrasion
condition of tires by said threshold set.
5. A program for judging road surface condition comprising: a
memory means for memorizing wheel rotational speed of each tires
mounted on a vehicle; a slip ratio-calculating means for
determining a slip ratio from said wheel rotational speeds; an
acceleration deceleration-calculating means for determining
acceleration or deceleration of said vehicle; a relation
equation-calculating means for determining a relation equation
between said slip ratio and said acceleration of the vehicle; a
judgment value-calculating means for determining a judgment value
for judging a friction coefficient between road surface and said
tires based on slope of said relation equation determined; and a
threshold-setting means for setting a threshold used for judging
friction coefficient from said judgment value with information of
wireless tags buried in said tires.
6. The program for judging road surface condition of claim 5
further comprising an abrasion-judging means for judging abrasion
condition of tires by said threshold set.
Description
BACKGROUND OF THE INVETNION
[0001] The present invention relates to a method for judging road
surface condition and a device thereof, and a program for judging
road surface condition. More specifically, the present invention
relates to a judging method of road surface condition which can
improve the performance and running safety of a vehicle by judging
the road surface and the abrasion condition of tires, and a device
thereof; and a program for judging the road surface condition.
[0002] There have been conventionally proposed an antilock brake
device and the like which lower braking torque which acts on wheels
before braking force between tires and road surface exceeds a
maximum value and the tires become in a lock condition, prevent the
lock condition of wheels, and control the rotational number of
wheels by which the maximum braking force is obtained (for example,
Japanese Unexamined Patent Publication No. 99757/1985 and Japanese
Unexamined Patent Publication No. 249559/1989). For example, the
friction coefficient of the road surface, .mu. is utilized in the
control of the antilock brake device, and an optimum control is
designed to be carried out by changing the content of control in
accordance with the friction coefficient of the road surface, .mu.
(road surface, .mu.), for example, between a case of high .mu. and
a case of low .mu..
[0003] As the friction coefficient of the road surface-judging
device which judges such road surface, .mu., there is a device
which determines a relation equation between a slip ratio and the
acceleration or deceleration of a vehicle, and then judges the
friction coefficient between the road surface and tires based on
the slope of said relation equation (Japanese Unexamined Patent
Publication No. 253334/2001). The road surface .mu. is designed to
be judged by the threshold of a linear regression coefficient, K1
between a slip ratio and the acceleration or deceleration of a
vehicle, for the slope.
[0004] However, since the threshold for judging the slipperiness of
the road surface is preliminarily input from past data, it is
required to input the threshold again when tires are replaced with
the different kinds of tires.
[0005] Then, there are a road surface condition-judging device
(Japanese Unexamined Patent Publication No. 274357/2002) in which
after a correlative coefficient and the linear regression
coefficient between a slip ratio and the acceleration or
deceleration of a vehicle are determined, the threshold of judging
the road surface condition is set based on the linear regression
coefficient when said correlative coefficient is a fixed value or
more, and a road surface condition-judging device (Japanese
Unexamined Patent Publication No. 118555/2003) in which after the
slip ratio of the front and rear wheels at left side to the front
and rear wheels at right side and the slip ratio of the front and
rear wheels are respectively calculated, the fluctuation quantity
of difference of said left and right slip ratios is calculated, and
then the threshold of judging the road surface condition is set
based on the linear regression coefficient between the slip ratio
of the front and rear wheels and the acceleration or deceleration
of a vehicle when said fluctuation quantity is a fixed value, and
the like.
[0006] Further, when tires are abraded, the thickness of tread
rubbers of tires becomes thin, therefore the back and forth
rigidity of a pattern becomes large. When tires are abraded, tires
for winter affect performance on snow and tires for summer affect
hydroplaning performance. Accordingly, it is also useful to detect
the abrasion. For example, as a road surface condition-detecting
device of judging that the abrasion of tires proceeds, there is a
device (Japanese Unexamined Patent Publication No. 36837/2002) in
which the abrasion of tires is designed to be detected by comparing
the mutual linear regression coefficient between the slip ratio and
the acceleration or deceleration of a vehicle with frequency
distribution which is preliminarily grasped.
SUMMARY OF THE INVENTION
[0007] However, for the road surface condition-judging device, when
tires were exchanged, the threshold is not immediately changed, and
a vehicle must run for a long time until the threshold is
changed.
[0008] Further, for the abrasion condition-detecting device, when
used tires were installed, the abrasion from new articles cannot be
detected, therefore when studless winter tires are installed for 2
to 3 seasons in winter, the proceeding degree of the abrasion
cannot be correctly judged.
[0009] Under the circumstances, an object of the present invention
is to provide a method for judging condition of road surface which
can judge the road surface and can improve the performance and
running safety of a vehicle by judging the abrasion condition of
tires, and a device thereof; and a program for judging the road
surface condition.
[0010] The judgment method of road surface condition of the present
invention is characterized by comprising steps of: periodically
detecting the wheel rotational speeds of the four wheel tires of a
vehicle, memorizing the wheel rotational speed of each of tires,
determining a slip ratio from said wheel rotational speed,
determining the acceleration or deceleration of the vehicle,
determining a relation equation between said slip ratio and the
acceleration or deceleration of the vehicle, determining a judgment
value for judging a friction coefficient between the road surface
and tires based on the slope of said relation equation determined,
and setting a threshold which is used for judging the friction
coefficient from the judgment value using the information of
wireless tags which were buried in the tires.
[0011] Further, the judgment device of road surface condition of
the present invention is characterized by being equipped with a
wheel speed-detecting means of periodically detecting the wheel
rotational speeds of the four wheel tires of a vehicle, a memory
means of memorizing the wheel rotational speed of each of tires, a
slip ratio-calculating means of determining a slip ratio from said
wheel rotational speed, an acceleration deceleration-calculating
means of determining the acceleration or deceleration of the
vehicle, a relation equation-calculating means of determining a
relation equation between said slip ratio and the acceleration or
deceleration of the vehicle, a judgment value-calculating means of
determining a judgment value for judging a friction coefficient
between the road surface and tires based on the slope of said
relation equation determined, and a threshold-setting means of
setting a threshold which is used for judging the friction
coefficient from the judgment value using the information of
wireless tags which were buried in the tires.
[0012] Furthermore, the program for judging road surface condition
of the present invention is characterized by functionalizing a
computer as a memory means of memorizing the wheel rotational speed
of each of tires, a slip ratio-calculating means of determining a
slip ratio from said wheel rotational speed, an acceleration
deceleration-calculating means of determining the acceleration or
deceleration of the vehicle, a relation equation-calculating means
of determining a relation equation between said slip ratio and the
acceleration or deceleration of the vehicle, a judgment
value-calculating means of determining a judgment value for judging
a friction coefficient between the road surface and tires based on
the slope of said relation equation determined, and a
threshold-setting means of setting a threshold which is used for
judging the friction coefficient from the judgment value using the
information of wireless tags which were buried in the tires, in
order to judge the condition of road surface.
[0013] According to the present invention, the generation of false
alarm can be prevented by changing the threshold which is the
judgment basis of slipperiness of the road surface by the
transmitting information of wireless tags. Referring to Examples
described later, the thresholds of tires B, C and D whose threshold
data are not preserved can be calculated as 0.126, 0.113 and 0.097
from the threshold of 0.098 which is memorized in tires A. The
threshold of judging the slipperiness of road surface is changed in
accordance with the kind of tires by the transmitting information
of wireless tags, a false alarm is not emitted at running on an
asphalt road, and an alarm is emitted at running on a porcelain
tile road having low friction coefficient, therefore the road
surface condition can be accurately judged.
[0014] Further, according to the present invention, the degree of
abrasion can be judged by comparing the judgment threshold of the
slipperiness of road surface which was changed by the transmitting
information of wireless tags, with the average judgment value in
tires installed. Referring to Example 2 described later, since the
judgment threshold of basic tires is 0.10 and the judgment
threshold of the slipperiness of studless winter tires is 0.13, the
average judgment value is nearly equal against the threshold of
basic tires when the average judgment value of the slipperiness is
0.11 (an abrasion of 25%) or 0.10 (an abrasion of 50%).
Accordingly, since it is small against the proper threshold of
0.13, it can be judged that abrasion proceeds.
[0015] According to the present invention, the optimum control in
accordance with the slipperiness of road surface can be carried out
by using the information of the slipperiness of road surface which
was judged as described above, to an ABS (antilock braking system)
device, a TRC (traction control) device and the like. Further, when
it was judged that the slipperiness is high, it can be informed
that a driver should take care of slippery road surface.
[0016] For example, the ABS device can set the upper limit of
brake-operating force in accordance with the slipperiness of road
surface by inputting the slipperiness of road surface during
running from the judgment device of road surface condition of the
present invention. The ABS device detects momentarily slip (tire
lock), and controls the brake-operating force in real time. The ABS
device can obtain the maximum breaking force just before tire lock
by setting the upper limit of the brake-operating force in
accordance with road surface condition, and safer and surer brake
can be realized. As a result, when a vehicle runs by installing
studless winter tires on road surface on which it began to rain,
road surface on which dust was washed off by rain, and road surface
on which it snowed (slipperiness differs depending on temperature),
brake control can be carried out in accordance with situation
between tires and frozen road surface or road surface such as a
pebble road.
[0017] The TRC device can realize the more effective drive control
of a vehicle by inputting the slipperiness of road surface from the
judgment device of road surface condition of the present invention,
for example, controlling the allotment of driving force of left and
right wheels, and preventing slip at take-off and acceleration by
setting the upper limit of driving force in accordance with the
slipperiness of road surface. For example, it can control a vehicle
to an appropriate driving force even on a snow slope way and can
avoid slip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a block chart showing the road surface
condition-judging device related to one embodiment of the present
invention.
[0019] FIG. 2 is a block chart showing the electric constitution of
the road surface condition-judging device of FIG. 1.
DETAILED DESCRIPTION
[0020] The judgment method of road surface condition and a device
thereof, and the program for judging road surface condition of the
present invention are illustrated below based on the attached
drawings.
[0021] As represented in FIG. 1, the judgment device of road
surface condition related to a embodiment of the present invention
is equipped with the usual wheel speed-detecting means 1 which were
provided respectively relating to four tires, FL, FR, RL and RR
which were provided on a vehicle.
[0022] As the wheel speed-detecting means 1, there can be used a
wheel speed sensor for generating rotational pulses using an
electromagnetic pickup and the like and periodically measuring
wheel rotational information such as rotational angular velocity
and rotational velocity from the number of pulses, or an angular
velocity sensor including those which generate power utilizing
rotation such as a dynamo and measure rotational angular velocity
and rotational velocity from the voltage. The output of the wheel
speed-detecting means 1 is provided to the control unit 2 being a
computer such as ABS. A display device 3 which is composed by a
liquid crystal display for informing tires whose air pressure was
lowered, a plasma display device or CRT and the like, an
initialization switch 4 which can be operated by a driver, and an
alarm unit 5 are connected with the control unit 2. Further,
wireless tags are buried in tires. As such wireless tags, for
example, V720-D52P30 (trade name, manufactured by OMRON Co.) can be
used. The reader 6 of the wireless tags is connected with the
control unit 2.
[0023] As represented in FIG. 2, the control unit 2 is composed of
an I/O interface 2a which is necessary for transferring signals
with external devices, a ROM 2c in which the control operation
program for said CPU 2b was stored, and a RAM 2d in which data are
temporarily downloaded and the downloaded data and the like are
read out when the CPU 2b carries out control operation.
[0024] The rotational speed-detecting means 1 outputs pulse signals
(hereinafter, referred to as wheel speed pulses) corresponding to
the rotation numbers of tires. Further, CPU 2b calculates the
rotational angular velocities, Fi, of the respective tires by every
fixed sampling cycle, .DELTA.T (sec), for example, by every
.DELTA.T=1 second, based on the wheel speed pulses which were
output from the rotational speed-detecting means 1.
[0025] By the way, since tires are produced including unevenness
(initial difference) within specification, the effective rolling
radii (a value obtained by dividing a distance proceeded by one
rotation, by 2.pi.) of respective tires are not always the same
even if all tires have normal air pressure. Accordingly, the
rotational angular velocities, Fi of respective tires come to be
uneven. Therefore, for example, there is a method of excluding the
influence of initial difference from the rotational angular
velocities, Fi. Firstly, the method calculates initial correction
coefficients K1, K2 and K3 which are shown as follows:
K1=F1/F2 (1)
K2=F3/F4 (2)
K3=(F1+K1.times.F2)/(F2+K2.times.F4) (3)
[0026] Hereat, F1 to F4 are respectively the rotational angular
velocities of a front left tire, a front right tire, a rear left
tire and a rear right tire. Subsequently, new the rotational
angular velocities, F1.sub.i are determined using the initial
correction coefficients K1, K2 and K3 which were thus calculated,
as shown in the equations (4) to (7).
F1.sub.1=F1 (4)
F1.sub.2=K1.times.F2 (5)
F1.sub.3=K3.times.F3 (6)
F1.sub.4=K2.times.K3.times.F4 (7)
[0027] Herein, the initial correction coefficient, K1 is a
coefficient for correcting the difference of effective rolling
radius which is caused by the initial difference between left and
right front tires. The initial correction coefficient, K2 is a
coefficient for correcting the difference of effective rolling
radius caused by the initial difference between left and right rear
tires. The initial correction coefficient, K3 is a coefficient for
correcting the difference of effective rolling radius caused by the
initial difference between a left front tire and a left rear tire.
Then, the wheel speed of a tire of each wheel, Vi is calculated
based on the F1.sub.i. In the present invention, the rotational
speed of a tire is a product of the rotational angular velocity of
a wheel with the effective rolling radius of the tire.
[0028] In the present mode of operation, the judgment device of
road surface condition is composed of the wheel speed-detecting
means 1, a memory means of memorizing the rotational speed of each
of tires, a slip ratio-calculating means of determining a slip
ratio (a ratio of the rotational speed of front tires to the
rotational speed of rear tires) from said rotational speed, an
acceleration deceleration-calculating means of determining the
acceleration or deceleration of the vehicle, a relation
equation-calculating means of determining a relation equation
between said slip ratio and the acceleration or deceleration of the
vehicle, a judgment value-calculating means of determining a
judgment value for judging a friction coefficient between the road
surface and tires based on the slope of said relation equation
determined, and a threshold-setting means of setting a threshold
which is used for judging the friction coefficient from the
judgment value using the information of wireless tags which were
buried in the tires.
[0029] For example, the road surface, .mu. is judged by the
threshold below (0.12 and 0.18), by setting the slope of the
relation equation as a linear regression coefficient, K between a
slip ratio and the acceleration or deceleration of a vehicle which
is the judgment value of road surface.
K.ltoreq.0.1 High .mu. road (.mu.=0.7 or more)
0.1<K.ltoreq.0.16 Medium .mu. road (.mu.=0.3 to 0.7)
0.16<K Low .mu. road (.mu.=0.3 or less) (8)
[0030] The threshold of the regression coefficient, K can be
obtained from the experimental data hetherto by every tire which
was preliminarily set.
[0031] In the present mode of operation, the rotational speeds of
tires of the four wheels are detected at 0.1 second or less, and
preferably 0.05 second or less. The acceleration or deceleration of
a vehicle can be determined by being measured with a G sensor, but
it is preferable from the viewpoint of cost that it is calculated
from the average rotational speed of the four wheels or coupled
driving wheels.
[0032] Then, the moving average of the slip ratio and the
acceleration or deceleration of a vehicle is determined as the
average of data for a fixed time, for example, data for 0.1 second
or more, by every sampling time, and the relation equation between
said slip ratio and said acceleration or deceleration of a vehicle
is determined based on the value of moving average (the slip ratios
of a fixed number and the acceleration or deceleration of a
vehicle).
[0033] Further, the mutual linear regression coefficient between a
slip ratio and the acceleration or deceleration of the vehicle, and
the correlative coefficient are determined using the data obtained
from the moving average of the slip ratios and the acceleration or
decelerations of a vehicle, for example, at least 5 or more of
data. Hereat, when the slip ratio which was obtained from the
moving average is a fixed value or more (for example, when it is
0.07 or more, or -0.07 or less), it is not used for the calculation
of regression coefficient, it may be alarmed as slip alarm.
[0034] In the present mode of operation, when it is input that
tires were exchanged, the discrimination information is obtained
from the wireless ID tags. The discrimination information is a
maker, a tire size, the kind of size and the like. For example,
when it recognizes studless winter tires, new threshold, SS is
calculated base on size information, maker information and the
like.
[0035] For example, when the threshold at a basis size and basis
tires (tires when standard installation is tires for summer) was S,
the new threshold SS can be set based on (1) to (4) below.
[0036] (1) It is lessened by 1% by every magnification of 10 mm of
the size of tire width.
[0037] (2) It is enlarged by 1% by every magnification of 10 mm of
the height of tires.
[0038] (3) It is enlarged by 25% when tires are studless winter
tires.
[0039] (4) It is enlarged by 12% when tires are tires for all
seasons.
[0040] Further, a correction coefficient, a can be also multiplied
depending on a maker or a pattern (for example, Winter Sport M3
manufactured by German Dunlop Co.). For example, it is .alpha.=1.0
in case of tires for summer, it is .alpha.=1.25 in case of the
studless winter tire and .alpha.=1.12 in case of tires for all
seasons.
[0041] Firstly, when the judgment value of road surface judged by
the judgment value-calculating means is larger than the threshold,
S, the judgment of road surface can be carried out when the
friction coefficient, .mu. of tire at installation is lowered.
[0042] When values after change of tire width and tire height are
respectively T' and H', the new threshold, SS can be represented as
follow.
SS=S.times.{1+(T-T')/1000}.times.{1+(H'-H)/1000}.times..alpha.
(9)
[0043] Then, the judgment of road surface is carried out by the new
threshold, SS in place of the equation (8).
[0044] Further, the new threshold, SS is compared with the judgment
value (for example, the value of the linear regression coefficient,
K) of road surface judged when a vehicle runs really on various
road surfaces. Firstly, when studless winter tires (used studless
winter tires) whose abrasion has proceeded are installed, the
vehicle at running on snow and ice is apt to slip more easily than
running at new tires, and it is dangerous. However, since it can be
detected by the judgment of road surface that it is apt to slip
easily, safe running can be carried out by alarming it to a driver.
To the contrary, when a vehicle runs on an asphalt road, the
judgment value for judging the slipperiness of road surface is
lessened because the stiffness of tread becomes higher caused by
abrasion, therefore the judgment value of road surface reveals a
value without slipping which does not exceed the new threshold,
SS.
[0045] Accordingly, when the judgment that there is no slip at
which the judgment value of road surface does not exceed the new
threshold, SS is frequently provided, it means that the abrasion of
studless winter tires has proceeded, therefore it can be grasped
that the abrasion condition of used studless winter tires (for
example, 25%, 30% or 50%) can be judged by comparing the new
threshold, SS with the judgment value of road surface.
[0046] Thus, the generation of false alarm can be prevented by
changing the threshold being the judgment basis of the slipperiness
of road surface according to the transmitting information of
wireless tags.
[0047] Further, the threshold at new articles of the studless
winter tires can be calculated from the information of kind of
tires by the information of threshold in tires for summer and the
information of wireless tags concerning the studless winter tires.
The abrasion condition of the tires can be deduced by comparing the
threshold at the new articles of the studless winter tires with the
judgment value of road surface when a vehicle runs on asphalt.
[0048] Then, the present invention is illustrated based on
Examples, but the present invention is not limited to only such
Examples.
EXAMPLE 1
[0049] BMW328i mounting a reader for wireless ID tags was prepared
as a vehicle. After tires having a tire size of 205/55ZR16 SP9000
(a tire width of 215 mm, an outer diameter of 631 mm and a tire
height of 113 mm) were installed as the basis tires, it run on the
Okayama Test Course of Sumitomo Rubber Industry Co., Ltd. (an
asphalt road with a friction coefficient, .mu. of nearly 1.0 and a
porcelain tile road with a friction coefficient, .mu. of nearly
0.1). The friction coefficient, .mu. is the maximum values for the
basis tires, respectively.
[0050] Then, the following four kinds of tires, A, B, C and D were
used as tires for test in which the wireless ID tags were
buried.
[0051] (1) Tires A
[0052] A tire size is 215/45R17 SP9000 (tires for summer: a tire
width of 220 mm, an outer diameter of 623 mm and a tire height of
96 mm).
[0053] (2) Tires B
[0054] A tire size is 205/55R16 DS2 (studless winter tires: a tire
width of 205 mm, an outer diameter of 633 mm and a tire height of
113 mm).
[0055] (3) Tires C
[0056] A tire size is 205/55R16 SP Winter Sport M3 (tires for all
seasons: a tire width of 215 mm, an outer diameter of 631 mm and a
tire height of 113 mm).
[0057] (4) Tires D
[0058] A tire size is 245/45R17 SP9000 (tires for summer: a tire
width of 250 mm, an outer diameter of 631 mm and a tire height of
112 mm).
[0059] The result of the running tests is shown in Table 1.
Further, the threshold of tires A is preliminarily retained at
0.098, and the thresholds of tires B, C and D whose threshold data
are not retained are respectively 0.126, 0.113 and 0.097 according
to the calculation of the equation (9).
1TABLE 1 Average Average judgment value judgment value at running
on at running on Threshold Kind of tires asphalt road porcelain
road (new threshold) Basis tires 0.09 0.18 0.10 Tires A 0.09 0.17
0.098 Tires B 0.11 0.22 0.126 Tires C 0.10 0.21 0.113 Tires D 0.09
0.17 0.097
[0060] It can be grasped from Table 1 that when the new thresholds
which were calculated from the information of wireless ID tags are
used with respect to the tires B, C and D, false alarm is not
emitted at the running on an asphalt road but alarm is emitted at
the running on a porcelain tile road therefore the condition of
road surface can be accurately judged.
EXAMPLE 2
[0061] BMW328i mounting a reader for wireless ID tags was prepared
as a vehicle. Then, after tires having a tire size of 205/55ZR16
SP9000 (a tire width of 215 mm, an outer diameter of 631 mm and a
tire height of 113 mm) were installed as the basis tires, it run on
the Okayama Test Course of Sumitomo Rubber Industry Co., Ltd. (an
asphalt road with a friction coefficient, .mu. of nearly 1.0). The
friction coefficient, .mu. is the maximum value (representative
value) for the basis tires.
[0062] Then, new articles and studless winter tires with an
abrasion of 25% and studless winter tires with an abrasion of 50%
were used as tires for test in which the wireless ID tags were
buried. Further, the tire size of the studless winter tires is
205/55R16 DS2 (studless winter tires: a tire width of 205 mm, an
outer diameter of 633 mm and a tire height of 113 mm).
[0063] The result of the running tests is shown in Table 2.
Further, the threshold according to running by the basis tires is
0.1, and the new threshold is 0.13 according to the calculation of
the equation (9).
2TABLE 2 Average judgment value at running on Threshold Kind of
tires asphalt road (new threshold) Basis tires 0.10 0.10 New
article tires 0.13 0.13 Tires with an abrasion of 25% 0.11 0.13
Tires with an abrasion of 50% 0.10 0.13
[0064] It can be grasped from Table 2 that the more the tires are
worn, the less the average judgment value is, and the proceeding
degree of abrasion can be judged by comparing them with the new
thresholds in accordance with tires installed which were calculated
from the information of wireless ID tags. As a result, the degree
of abrasion can be judged in accordance with tires installed, and
it can be alarmed to a driver that the degree of abrasion has
proceeded and tires are slippery.
[0065] According to the present invention, the performance and
running safety of a vehicle can be improved by reading information
concerning the discrimination of tires by the transmitting
information of wireless tags, and changing the threshold which is
the judgment basis of slipperiness of the road surface based on the
information.
[0066] Further, the abrasion condition of tires can be judged by
comparing the threshold with the really calculated judgment value
which judges the slipperiness of road surface, and when it is
judged that abrasion has proceeded, running safety can be
heightened by urging a driver to exchange tires.
[0067] It is to be understood that the above-described arrangements
are only illustrative of the application of the principles of the
present invention. Numerous modifications and alternative
arrangements may be devised by those skilled in the art without
departing from the scope of the present invention, and the appended
claims are intended to cover such modifications and
arrangements.
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